An optical switch is a device that selectively couples light beams from input fibers to output fibers. An optical switch typically includes an optical switching core having miniaturized moveable mirrors that redirect light beams from input fibers to desired output fibers without conversion to electrical signals. A problem that can occur in an optical switch is component failure that can cause optical signal loss. To address component failure, an optical switch may include redundant optical switching cores (“switching cores”). That is, an optical switch may have an alternative switching path from a main switching core to a backup switching core in the event of a component failure to the main switching core.
Thus, an optical switch having redundant switching cores must provide an alternative path for an optical input. Furthermore, for proper coupling within an optical switch, an optical beam must enter or leave an optical fiber in a direct path. FIG. 1 illustrates a prior art 1×2 optical switch 100 having separate, discrete angled lens holders 160-1 through 106-3 for each separate optical fiber (e.g., IN1, OUT1, OUT2). A light beam leaving IN1 can thus travel along two alternative switch paths via OUT1 or OUT2 such that optical outputs OUT1 and optical output OUT2 can be directed to different switching cores.
Referring to FIG. 1, prior optical switch 100 includes one input fiber 108-2 for optical input (IN1) and two output fibers 108-1 and 108-3 for optical outputs (OUT1 and OUT2), and a substrate 102 supporting a moveable mirror 104. Moveable mirror 104 redirects a light beam from optical input IN1 to either optical output OUT1 or optical output OUT2 through separate lenses 105-3 or lens 105-1 in a direct path. In prior optical switch 100, the separate lenses 105-3 and 105-1 are held in separate lens holders 106-3 and 16-3, which have to be separately aligned to provide a direct path for light beams to enter into optical outputs OUT1 and OUT2.
A disadvantage of using prior optical switch 100 is that a separate lens holder (106-1 through 106-3) is needed for each optical input and output. In particular, requiring separate lens holders for each optical input or output increases fabrication costs. Another disadvantage of using prior optical switch 100 is that each lens holder must be separately aligned to provide a direct path for a light beam to enter a corresponding optical fiber. This increases the complexity for fabricating optical switches, especially if there are a large number of optical inputs and outputs. Another disadvantage of using prior optical switch 100 is that the lens holder is positioned in a curved manner around moveable mirror 104, which can be complicated to fabricate.
Another type of prior art optical switch providing alternative switch paths for an optical input is described in “A Rotary Electrostatic Micromotor 1×8 Optical Switch,” by Yasseen et al., IEEE Journal of Selected Topics in Quantum Electronics, vol. 5, no. 1, January/February 1999. This type of 1×8 optical switch uses a rotary mirror in which output fibers are positioned around the rotary mirror to provide a direct path for an optical beam from an optical input that is redirected from the rotary mirror. Similar to prior optical switch 100, a disadvantage of this type of optical switch is that the output fibers have to be separately aligned, which can cause the fabrication of such an optical switch to be difficult and prevents increased capacity for coupling of optical fibers.
Optical protection switches may be implemented in a variety of ways each having advantages and drawbacks. When implementing an optical switch as a protection switch in an optical switching system, it is important to keep the loss through the optical switch as low as possible to minimize total path loss.